I think part of the key here is that there are not nearly as many stupid players at that level of stakes that would go all-in thinking they have the nuts with a flush or a full-house. If you were an expert cash-ring player would you go all-in with an Ace-high flush with two aces showing and a tight player who raised pre-flop. Would you risk 12k to find out if your twos full of aces was still good. There is an equal chance that somebody has the 34 of spades as two aces after the cards are on the board. A strait flush is no longer extremely rare after you factor in the fact that 3 of the cards needed are on the board. After this board shows up four aces vs a strait flush is no longer a one in a million situation.